Although cardiovascular stress tests have in the past usually been restricted to physical exercise, there is increasing evidence that the hemodynamic response to certain nonexercise stresses such as change in posture, increased intrathoracic pressure and local cold can serve as valuable indicators of circulatory function. Because of the prominent role of physical exercise in the prevention and treatment of heart disease, the possible effect of training on tolerance to nonexercise stress is a related important question. This is particularly true in the elderly who are more vulnerable to such environmental stresses. The very limited data thus far available on such cross-adaptation is conflicting. Previous studies indicate decreased response of older persons to both exercise and nonexercise stresses, but the mechanism of this decline is poorly understood. A complicating factor is that stress studies to date have been done predominantly on men; however, recent evidence indicates significant differences in such reactions between men and women. It is evident that, aside from the question of cross-adaptation between exercise and nonexercise stress, the influence of age and sex on the autonomic response to these stresses requires further study. The primary objective of our proposed study will be to compare the acute hemodynamic responses of physically trained and untrained healthy women of three age groups (20-29, 40-49 and 60-69 years of age) to several circulatory stresses, i.e., graded headup tilt (postural stress), graded Valsalva tests (increased intrathoracic pressure) and local cold (thermal stress). Responses will be monitored by noninvasive methods such as impedance cardiography and strain gauge plethysmography. These results will be compared with those of similar studies in male subjects (now underway in our lab). In follow-up experiments, the physical training effect will be further explored by means of lower body negative pressure and carotid baroreflex tests. The purpose of this phase will be to study the autonomic mechanisms involved in these responses.